Short answers, pulled from the story.
Native Americans used a wide variety of styles and techniques, with the flute and many kinds of percussion instruments like drums, rattles, and shakers forming the core of their instrumentations. These early traditions often lacked harmony or polyphony, relying instead on vocables and descending melodic figures.
Antonín Dvořák visited the United States from 1892 to 1895 and urged that American classical music needed its own models instead of imitating European composers. He encouraged composers to develop indigenous styles rather than following European examples.
Blues developed in the rural South in the first decade of the 20th century as a combination of African work songs, field hollers, and shouts. The most important characteristics of the blues are its use of the blue scale with a flatted or indeterminate third.
Berry Gordy founded Motown in 1959 in Detroit, Michigan. It was one of few R&B record labels that sought to transcend the R&B market and specialize in crossover music while producing music of black American roots that defied racial segregation.
Seattle's local scene produced grunge music which became wildly popular across the United States in 1991. Bands like Nirvana, Pearl Jam, Soundgarden, and Alice in Chains added a more melodic element to the sound.